鐵-30wt.%錳-10wt.%鋁-1.0wt.%碳氣體氮化後其 機械性質和在⼈體模擬液中之抗腐蝕性研究

Abstract

鐵-30wt.%錳-10wt.%鋁-1.0wt.%碳合⾦在淬⽕狀態下，其顯微結構為單⼀ 沃斯⽥鐵相，無任何析出物。將淬⽕狀態合⾦經550℃氣體氮化5 ⼩時，結 果產⽣約47μm 厚度的氮化層，氮化層主要為⾯⼼⽴⽅結構氮化鋁(AlN)， 其體積百分率為84.3%，氮化層表⾯氮濃度⾼達17.9wt.%(43.3at.%)，表⾯ 硬度⾼達1814Hv。氮化處理使沃斯⽥鐵基地內有緻密細⼩的κ'-碳化物析出， 因此氮化合⾦具有優異的機械性質合(YS 為1024MPa)和延性(El.為77%)組 合。氮化合⾦在⼈體模擬液(SBF)中極化試驗結果顯⽰有明顯的鈍化區，其 腐蝕電流(Icorr)、孔蝕電流(Ipit)、腐蝕電位(Ecorr)、孔蝕電位(Epit)和鈍化區電 位差ΔE (Epit-Ecorr)分別為5×10-9 A/cm2、5.1×10-7 A/cm2、+5 mV、+1809 mV 和+1804 mV。本氮化合⾦無論強度、延性和在⼈體模擬液中的極化抗蝕性 均遠優於廣泛⽤在⼈體內經過表⾯處理的316L 不鏽鋼。

The microstructure of the Fe-30wt.%Mn-10wt.%Al-1.0wt.%C alloy in the as-quenched condition is a single-phase austenite(γ) without any precipitates. When the as-quenched alloy is gas-nitrided at 550°C for 5 hours, resulting in a 47 μm-thick nitrided layer. The nitrided layer consists predominantly of FCC AlN. The volume fraction of AlN reaches to 84.3%. Therefore, the nitrogen concentration at surface is extremely high up to 17.9 wt.% (43.3 at.%), leading to a very high surface hardness of 1814 Hv. Additionally, a high density of fine κ'-carbide is formed within the γ matrix during plasma-nitriding treatment. Consequently, the nitrided alloy exhibits an excellent combination of strength (YS: 1024MPa) and ductility (El: 77%). The potentiodynamic polarization examination for the gas-nitrided alloy in Simulated Body Fluid (SBF) solution appears an apparent passivation region. The corrosion current density (Icorr), pitting current density (Ipit), corrosion potential (Ecorr), pitting potential (Epit) and ΔE (Epit-Ecorr) are 5×10-9 A/cm2, 5.1×10-7 A/cm2, +5 mV, +1809 mV and +1804 mV, respectively. Compared to the surface-treated 316L stainless steels for implant application, the strength, ductility, and the corrosion resistance in SBF of the nitrided alloy are far superior to those obtained previously in optimally surface- treated 316L stainless steel.